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Figure

A. First total synthesis of (±)-heliannuol A. B. First total synthesis of (±)-heliannane.

All the synthesis mentioned end up with racemic mixtures. In spite of the high importance of getting enantiopure compounds, the first report of an enantioselective total synthesis of heliannuols A and D have not been published until recently.47 The key point of the synthetic strategy was to get access to the enantiopure epoxide 35. Base-catalized intramolecular cyclization led to the desired heliannuols A and D in enantiopure forms.

MCPBA

Na2HPO4 DCM OMe 26

MCPBA

Na2HPO4 DCM OMe 26

OMe 27

1. KOH, DMSO, 70-100°C
2. NaSEt, DMF, ref.
3. KOH, DMSO, 70-100°C
4. NaSEt, DMF, ref.